Controller



Marfl 17, 1953 H. BoWDlTcH CONTROLLER 9 Sheets-Shea?I l Filed Aug. 2l, 1945 Increase 35 35a /Z Alrgly Manual Conrol March 17, 1953 H. BowDrrcH 2,631,570

CONTROLLER Filed Aug. 2l, 1946 v 9 Sheets-Shoe?I 2 Supply In' 62 I l7fI3 "BY I @QW/@mw March 17, 1953 H. L. BowDlTcH CONTROLLER Filed Aug. 2l 1946 l INVENTOR HOBZY L. owol'z'zaA ATTORNE s i March 17, 1953 H. L. BQwDrrcH 2,631,570

CONTROLLER Filed Aug. 21, 194e v 9 sheets-sheet 4 412 :il v` 9 /0/ INVENTOR.

March 17, 1953 H. L. BowDlTcH 2,631,570

CONTROLLER Filed Aug. 21, 194e 9 sheds-sheet 5 Direct Open 8 Shut From Manual Regulator INVENTOR ATTOR YS March 17, 1953 H. l.. BowDlTcH 2,631,570

CONTROLLER 9 Sheets-Sheet 6 Filed Aug. 21 1946 4 INVENTOR.

BY @LM/A12 y ATTO HYS 2 l 2 '.-A 1: g

March 17, 1953 H. BowDlTcH 2,631,570

CONTROLLER Fied Aug. 2l; 1946 9 Sheets-Sheet 7 -Exhaust to March 17, 1953 H. L.. BowDlTcH CONTROLLER 9 Sheets-Sheet 8 Filed Aug. 2l, 1946 eww..

l INVENToR. Hoef L. owaz'c/z y WN www ma @E March 17, 1953 H. L. BowDlTcH 2,631,570

CONTROLLER Filed Aug. 21, 1946 '9 sheets-sheet 9 INVENTOR Hoez z. owddc/L BY @hug/Al Mlaga/:m9

TTOR EYS Patented Mar. 17, 1953 f,

CONTROLLER` Hoel L. Bowditch, Sharon, Mass., assignor to The Foxboro Company, Foxboro, Mass., a corporation of Massachusetts Application AugustI 21, 1946, Serial No. 692,102

28 Claims.

- 1 This invention relates to pneumatically operated instruments used in -connection with meas- -uring and/or controlling variable conditions of industrial processes.

Industrial processes utilize devices to measure variable conditions Asuch as temperature, pressure, flow, chemical concentration, etc., and generally utilize control apparatus to maintain such variable conditions at a desired value by manipulating some variable such as flow of liquid, heat, cold, etc. which affects the controlled variable. Y

It is an object of the present invention to provide improved apparatus for measuring and/or "controlling such variable conditions.

. A further object is toprovide improved apparatus capable of measuring and controlling industrial processes requiring a high degree of accuracy of measurement and control, and which apparatus is readily and simply applied to various processes.

' A further object is to provide such apparatus which requires a minimum of factory adjustments and which may be serviced in the field with a minimum-requirement of skilled labor.

y :A further object is to provide control apparatus which, while connected to the process, may be Yreadily shifted from automatic to manual control and vice versa.

, These and other apparent objects andadvan- .tages of this invention are obtained by the means described in the following specification and may Abe more readily understood by reference to the accompanying drawings wherein:

Figure 1 is a frontv elevation of measuring and .control apparatus embodying the present invention and shows a so-called direct action adjust- .ment ofthe control-ler; l Figure 2 shows diagrammatically certain parts of the control apparatus of Figure 1, the parts .being separated one from another in the drawing for purposes of explanation, but being pneumatically and mechanically connected together .to operate. in the same manner as is the control .apparatus of Figure 1;

Figure 3 is a perspective view of movement and .follow-up assemblies of the control apparatus shown in Figure 1, and showsa so-called reverse action adjustment of the controller;

f.V Figure 4 is a detail horizontal section taken on line 4-4 of Figure 1, but with the reverse action adjustment of Figure 3, and shows details of :the .movement assembly and of the bearings supfporting a oating lever:

, Figure 5 isa Vdetail vertical section taken on industrial process.

line 5 5 of Figure 1 but with the reverse action adjustment of Figure 3, and shows mechanism for adjusting the proportioning band of the control apparatus of Figure 1, the bellows assembly, and further details of the iioating lever of Figure 4;

Figure 6 is a detail section taken on line 6-6 of Figure 4, and shows details of a dapper-nozzle mechanism;

Figure 6B (Sheet 9) shows in three views three extreme adjustments of the nozzle-apper mechanism;

Figure 7 is a detail vertical section taken on line '1 -l of Figure 4, and shows the movement assembly, floating lever, and bellows construction ingreater detail;

Figure 8 shows diagrammatically how the control apparatus of Figure 1 may be connected up to control the liquid level of a process;

Figure 9 is a detail side view of a pen-arm supporting shaft;

Figure 10 is a detail front view of the pen-arm supporting shaft of Figure 9;

Figure 11 is a detail vertical section taken on line I I-I I of Figure 9;

Figure 12 is a section taken on line l2-I2 of Figure 5, and shows a relay valve with an outer cover plate removed;

Figure 13 is a section taken on line |3|3 of Figure 5, and also showing the relay valve;

Figure 14 is a horizontal section taken on line M-IA of Figure 1, and shows further details of the relay valve;

, Figure 15 is a section taken on line l5-I5 of `Figure 14, and shows details of a restriction supplying the nozzle of the control apparatus of Figure 1 with a restricted ow of air;

Figure 16 is an exploded View of the relay valve and its support, and shows the passage in the support;

Figure 17 is a detail section taken on line I'l--H of Figure 1, and shows the nozzle construction and mounting;

Figure 18 is a diagrammatic view showing three 'positions of a transfer switch used in the apparatus of Figure 1 to pneumatically connect parts of the apparatus in diiferent ways (a fourth posi- ,tion being shown in Figure 2); and

Figure 19 is a detail vertical view of the diaphragm of the relay Valve.

Before describing the controller of Figure l, reference will be made to Figure 8, and to a brief description of problems involved in controlling an In Figure 8, a liquid level process is diagrams rnatically shown comprising a tank a, having two inlet pipes b and c, and an outlet pipe d provided with a restriction e. Liquid flows into tank a through both pipes b and c. The now through the pipe b may be varied by means of a hand valve f, and represents a variable load that may be placed on the process. The liquid flow into the tank through pipe c may be regulated by a conventional pneumatically-operated diaphragm motor valve g. The diaphragm motor valve g is operated by a pneumatic output control pressure from a control instrument h which, in response to the hydrostatic head in the tank a, converts an air supply to the controller into a pneumatic output control pressure.

In this process the flow of liquid outof the tank through the outlet pipe d at any moment depends upon two factors: (l) the liquid level (hydrostatic head) in the tank a which is the controlled variable, and (2) the amount of iixed restriction e in the outlet pipe d. The greater the hydrostatic head in the tank a, the greater will be the outflow through the pipe d.

Under equilibrium conditions, the ow out through the pipe d will equal the inflows through the pipes b and c. In other words, a hydrostatic head is established in the tank a sufficient to makethe outlet flow d equal the sum of the inows b and c. In this process it is desired to control the level in the tank a at a level designated by the arrow k, and at this level the low out through the pipe d is always the same,

The flow into the tank a through the pipe b is normally anuncontrolled flow, i. e., one that arbitrarily changes and so represents the change of load or demand placed on the process, and over which the controller h has no control. The flow through the pipe c is the flow regulated by the controller, and so is the manipulated variable i. e.,"the variable that is changed in order to make the total flow into the tank d that which is required to hold the level at the value lc, regardless of the load placed on the process. Thus, variation inthe flow into the tank through the pipe b varies the demand on the process, and varies the value which the controller will have to maintain theA manipulated ow through pipe c tohold the level at the desired value.

The varying degrees of diiiiculty of controlling processes such as is diagrammatically shown in Figure 8, and of controlling related processes containing more tanks and connecting resistancea'is discussed in the Philbrick Patent 2,360,889, issued Octberf24, 1944. It is sulicient to point out in this s'pecication thatthe problem of controlling with the desired accuracy difiicultly controlled processes has to some extent been solved by controllers such as disclosed in the Mason Reissue Patent 20,092, inthe above-mentioned Philbrick patent, and in the Mason application Serial No. 385,493, led March 27, 1941, now Patent No. 2,476,104, issued July 12, 1949.

Y One of the ever present problems, however, in the'manufacture of such controllers is that of eliminating Lfriction Vand dead space which seri- 'ouslyradversely affect the overall performance of control instruments. It is another object of the present invention to provide improved mechanism in which manufacturing costs are reduced without introducing into control mechanism objectionable friction or dead space.

Referring now to Figure 1, the controller there shown may be readily adapted to control many different types of industrial processes, and in the present description will be described as control- Iingthe liquid level of the process shown Figure 8. In Figure l, a measuring element I 0 is made responsive to the liquid level in the tank a of Figure 8. Through linkage mechanism of a movement assembly generally indicated by I I, the element operates a pen arm I2 which moves over a circular chart 9, of which only a fragment is shown, and indicates the value of the liquid level at all times.

The movement assembly II is connected by a link I3 to a iioating lever generally indicated at I4 of a control assembly generally indicated by I5. The control assembly I5 is pneumatically operated, and the output of its operation is pneumatic output pressure which goes to the diaphragm motor g of'Figure 8.

Because so many of the operating parts in Figure lare hidden one behind the other, reference will now be made to Figure 2 for a general discussion of and the operation of the parts of the instrument of Figure 1. The measuring element I0`is conventional and comprisesiaspiral hollow tubing. It has one end ma iixed with respectto aback plate 53 supporting the instrument, and a movable end Ib. Variation of-fiuid pressure inside the hollow elementi@ causesthe movable end E05 to move; i. e., with increase of pressure it moves clockwise, and with decrease of pressure it moves counterclcckwise.

The interior of element I0 is connected by tubing Ille to a conventional pressure transmitting device Id which may be placedin the bottom of the tank a of Figure 8, Variation of the hydrostatic pressure at the bottom of the tank a lexes a diaphragm 10e covering the device Id, and varies the pressure'of theffluidin-tubing |00. The free end I0b thereby assumes positions proportional to the level of the liquid in tank a.

The measuring element I0 has conveniently secured with respectv to its'free end Ib a lever If which is part of a bell crank and which moves with the free end Ilb as shown in U. S. Patent 2,209,910 issued to C.' VD. Young. The lever IUf is connected by a link I6 to arm I'If of a lever assembly generally indicated at I'I, and pivoted about axed axis .Ll- A. The lever vII vhas a forwardly eXtending-L-shaped arm I8 which carries pen arm I2, Figure l.

LeverI -is connected by a link I9 to*` dinerential bell crank 20, pivoted about'a floating axis B-B and supported by a supporting frame 2| also pivoted about the axis AA. vThe details ofthe lever I'I and crank 20 and the supporting frame 2I are shown in Figures 3, 4, '7, and 9-11, and will be described in detail following the present thumbnail sketch of the instrument.

The bell crank 20 is so connected by the link I3 to a `floating lever generally indicated at I4 of the control assembly I5, that the'horizontal position of the upper end I4a of the floating lever I4 is at all times caused to assume a position corresponding to the deviation of the level of the liquid in the tank a from the set'point of the controller-as determined by the location of the axis ofthe crank 25 as vwill be described (Figure 8). The floating lever I4 carries a pin 22 which operates a valve-operating lever 23, fixed to and supported by a shaft 24 and urged against the pin 22 by a hair spring 25.

The shaft 24 has fixed to it and supports a flapper valve 26, which cooperates with a nozzle 21 of a conventional nozzle-dapper valve assembly such as 'described in the Philbrick Patent 2,360,889. `The nozzle 21 is supplied with a restricted flow of air through a passage 28, a nozzle *volume 28a, a passage 28o, a restriction generally indicated at 29, and a supply chamber 30 forming part of a relay valve generally indicated at 3|. Air is conducted to chamber 30 by apipe 32 which connects with a transfer switch generally indicated at 33, and the transfer switch 33 is connected with the main air supply pipe 35 by a pipe 34.

As will be described in greater detail, the flapper-nozzle 26--21 varies the air pressure in a chamber 36 of the relay valve 3|, and in so doing varies the pressure on a diaphragm 31 thereof with the result that the output pressure of the relay valve varies with the operation of the dapper-nozzle valve 26-21. The output pressure ofthe relay valve goes through apassage 38, a pipe 39, to the transfer switch 33, and is conducted from the transfer switch through a pipe 46 and a passage 4| to a proportioning or follow-up bellows 42 of a bellows assembly generally indicated at43. The output pressure from the relay valve is conducted also to the diaphragm motor valve g through a pipe 48, and the output of the relay valve is the output pressure of the controller.

As will be described in greater detail, when the ilapper valve 26 moves further to cover the nozzle 21, thereby further restricting the flow of air from the nozzle 21, pressure builds up back of the nozzle 2 and in the chamber 36 of the relay valve 3|, whereupon the relay valve operates to increase the pressure in the passage 38, the pipe 39, the pipe 46, and in the proportioning bellows 42. Movement of the flapper valve 26 away from the nozzle 21 causes a reduction of the pressure back of the nozzle, and causes the relay valve to reduce its output pressure by exhausting more air to atmosphere throug an exhaust port 44, and reducing the air ow to passage 38 from the air supply chamber 30. This action serves to reduce the pressure in the proportioning bellows 42.

As described in the Philbrick patent, the nozzle 21 emits only a small jet of air, and the movement of the baille 26 with respect to the nozzle required to produce change of pressure back of the nozzle to operate the relayY valve to produce a maximum change of output pressure is preferably less than .001 of an inch. So long as the flapper is within this .001 of an inch of its travel from the nozzle, it `is considered to be within its operating range, and to be tangent to the nozzle. -The 'proportioning bellows 42 is opposed by a reset bellows 45. lows 42 and 45 are fixed, but their'inner opposing ends are free and operate against a flexure spring 46, rigidly secured at its end 46a. The flexure spring 46is so arranged that its free end 46h moves under the differential force exerted by the pressure in the proportioning bellows 42 and the pressure in the reset bellows 45. The flexure spring provides a spring characteristic in addition to the inherent spring characteristic of bellows42 and 45; and for every pressure difference existing in the bellows, the free end of the'flexure spring assumes a position corresponding to the pressure difference. The effective operating areas of the bellows 42 and 45 are equal so that when equal pressures exist in the bellows, the free end 46h is always positioned at the neutral (norm) position, axis D-D. n

The free end 46D supports ashaft 41 to which is secured the lower end |4b of the floating lever |4. This arrangement provides for operating the lever .t4 abevts end |412 s0 ihatiherppeeed The outer ends of the bel- Y element I0; and the lower end |4b is movable.

vertically by the bellows assembly. Thus the motion of pin 22 carried by the floating lever I4 may be considered as the resultant of two components of motion substantially perpendicular to each other, one from the measuring element Ill, and theother from the proportioning bellows.

Vertical movement of the floating lever by the proportioning bellows 42 causes the pin'22 carried by the floating lever to operate the flapperoperating arm 23, and so to operate flapper valve 26. The reactions of the flapper-nozzle 21-26, relay valve 3|, and the proportioning bellows 42, are such as to maintainV the ilapper 26 tangent to the nozzle 21 in the same manner as described in the Philbrick patent. If the pin 22 is holding the flapper 26 too far from the nozzle 21 within the .001 inch range of operation, the reaction of the relay valve 3| and proportioning bellows 42 is to lower the floating lever i4, and the pin 22 to establish the correct nozzle-dapper rela` tionship. If the pin 22 is holding the apper too close to the nozzle within the operating range, then the reactions are such as to raise the pin to establish the correct nozzle-dapper relationship.

Since the pin 22 is also moved by the measuring element I6, the result of the interaction or'- the parts is to cause pressure in the bellows 42 to change in accordance with changes in the position of the measuring element Hl, i. e., as moves the measuring element, so move the bellows 42 and the exure spring 46.

With the adjustment of the parts as shown in Figure 2, a direct action type of operation is obtained in which increasing pressure in the measuring element produces increasing output pressure of the controller. Now, as the pressure in the measuring element I0 increases, thereby moving the end |406 of the floating lever |4 to the right and so moving the pin 22 to the right, the flapperoperating arm 23 is turned clockwise by the pin 22, thereby tending to cause the apper 26 to cover the nozzle 21. But as this action takes place, the relay valve 3| increases its output pressure, and the pressure in the bellows 42, thereby causing the floating lever |4 to rise and the pin 22 to rise to counteract the clockwise action of the dapper-operating arm 23, whereby the tangency between the nozzle and the flapper is maintained at all times. This action causes the pressure in the bellows 42 to increase incorrespondence with movement of the measuring element.

The actions and reactions of the nozzle-flapper, the relay valve 3|, and the proportioning bellows 42 are made so fast that for all practical purposes any changes in position of the measuring element |0 are immediately and completely reflected accurately. and correspondingly in change of pressure in the bellows 42; and any rate of'change of position of the measuring element I0 is reflected in a corresponding rate of change of pressure in bellows 42.

This description of the operation omits from consideration the effect of bellows 45, and in fact the bellows 45 may be omitted, in which event the controller operates as a proportional controller as just described. The operation of a proportional controller, as more fully described in the above-mentioned Mason Patent 2,476,104, serves to make changes in the output pressure of the controller proportional to change of the condition being controlled.

g .The instruments ofFguresland 2, with ,the reset bellows in operation, is a proportoningplus-floatingcontroller, and as described in the above-mentioned Mason patent, this controller has the added feature over and above that of the proportioning controller of causing the process to balance out at a so-called set point value, regardless of the demand placed onthe process. The set point is that particular value of temperaturapressure. flow, etc. that the proportioning-plus-iloating controller will maintain regardless of the demand on the process.

. Still referring to Figure 2, the interior of bellows 42 .is connected with the interior of the bellows A115 .through a passage 49, a restriction generally indicated at 59, and a passage l. The restriction illustrated is a variable restrictor of a' construction described and claimed in the Bilyeu patent application, Serial No. 559,640, led October 20, 1944, now Patent No..2,432,082. The variable restriction comprises a bent tube 50a having a attened oroval cross-section and having one. end mounted in a xed base 5%. The tube 50a may be bent to diierent curvatures `by a movable base 50c anda manually operable lever" 50d. A freely flexible return tube .59e connect the movable block 5Elc with base 5G17, Yand with the passage'l. By changing the curvature of= the tubev 5mi, the restriction that it Oilers to the flow of air through it changes. The tighter its curvature, the more restriction it oiers, and vice versa.

When equal pressures exist in the bellows l2-v and 45, the free end 4Gb of the ilekure spring alwaysassumes itsv` neutral position at the axis D-D. In order to have the nozzle and flapper in their tangent relationship when the free end 45h is in vits neutral position, the measuring element lil must have the upper end lil-a of the oating lever in a corresponding neutral position at the axis E-E. When the oatng lever I4 is positioned such that its ends Hic and Mb are at their neutral positions, then the'pin 22 is in `a neutral position at the axis and the controller mechanism is Vat its control pointsetting positi-on.

The position ofthe end 14a is determined vby the-setting of the axis B-B of the frame 2l, as Will be described, and bythe position of the measuring element lil. For any given setting of the axis B-B, when the measuring element ID holdsl the end 14a at the neutral position, the valuel of the condition that holds the measuring element in this position corresponds with the control point setting or the set point of the instrument. The mechanism'by which the axis B-B is'adjusted, is referred to as the control point setting mechanism, and this mechanism will be described later.

Reference will now be made to Figure 8 and to Figure 2 `for a brief discussion of the operation of the controller as a, proportioning-plus-reset controller'. Assuming the direct action adjustment of the controller as shown' in Figure 2, and a control point setting adjustment to make the height k the'value of the control point setting, and assumingan equilibrium condition in which the level is balanced at if under these conditions the demand on the process is changed by increasing the ow into the tank through the pipe b, then the liquid level will start rising. As the level rises, the controller acts to increase the pressure on the diaphragm valve g thereby further closing the valve in the pipe vc so that as the level rises less and less 'water flows through the pipe c. This action will not only prevent thel level fromV rising as far as it wouldhad no controlaction been made, but will tend to return the level toward its control pointvalue. And eventually the controller will establish a pressure on the diaphragme! such as to balance out the process with the level at the original value of k.

The reason that the controller operates to bring the level back to the control point and doesnot permit it tobalance out above or below the control pointis fully described in the abovementioned Mason application, and so Ywill only be briefly traced inthe present specification.

When the measuring element l0 is at its control point.position,.it'holds the end Ma of the floating lever I4 at Vits neutral .position on the axis E-E, and the pressures in the two bellows 42.

and45 are equal and must be so in order properly to position the Vpin 22 on its aXis F-F, which position of the pin holds the ilapper in its tangent position.

.Assuming Aagain the upset caused by increasing the low through the pipe b, following the equilibrium condition; this results in the level in the tank :a starting to rise because more liquid is flowing into the tank than out of it. The rising level causes the measuring element l0 to assume a rate of change ina clockwise direction, andthe end ma of the floating lever I4 and pin 22 to assume a corresponding movement to the right. The resulting clockwise movement of the apperoperating arm 25 is oiTset by the reaction of the nozzle-dapper, the relay valve 3l, and the proportioning bellows 42 which served to move the pin 22 upwardly to lcounteract the rightward movement of the pin 22 and to keep the nozzle and dapper in their tangent relationship. The overall result is that the pressure in the bellows i2 assumes a rate of change corresponding with the rate of increase of the level in the tank a. rhis increasing pressure change which is transmitted to the diaphragm motor-y serves to give the valve in the pipe C a rate of closing. We can assume that the closing action of the valve eventually stops the level in tank a from rising, but unless some additional action isY performed the level would not return to its original value because, as the `level returned the controller would give the valve in pipe c an opening action. It is the reset actionV that permits and causes the controller to reestablish the set point value of the level.

If we assume that the pressures in the bellows 42 and 45u/ere equal and at a value of 8 lbs. before the upset of the process occurred, then when the upset occurredthe pressure in the bellows 42 immediately started increasing above the 8 lbs. in order to move the oating lever I4 -upwardly in order to keep the nozzle and apper tangent. And at any instant the amount that therpressure in bellows 42 was above that in bellows 45, corresponded with the amount that the measuring element l0 had moved the floating end Illa from its neutral position. But the pressure in the bellows 42 being higher than that in the bellows 45 causes air to flow through the restrictor 50 into the bellows 45, thereby causing pressure in the bellows 45 to assume a rate of increase, which rate of increase is proportional to the pressure difference between bellows 42 and 45. 1The increasing pressure in the bellows 45 causes a corresponding increase of pressure in the bellows y42, for the reason` that in order to hold the nozzle-dapper in a tangent relationship the pressure in the bellows 42 must be above that bellows 42 at the same rate.

vinthe bellows 45 by an amount corresponding with the amount that the measuring element I has moved away from its control point position. The rate at which the pressure in bellows 45 increases is, therefore, related to the deviation of vthe level 7c from its control point value. Thus, there are two factors now causing an increase of the pressure on the diaphragm motor g: (1) the rising 4liquid level (the proportioning control action); and (2) the increasing pressure in the bellows 45 caused by the deviation of the level from the control point value (the resetcontrol action) When the level in the tank a stops rising as a result of the closing action on the valve g and commences to lower, the pressure in bellows 42 responds by tending to decrease in the same way the pressure increased while the level was rising. But so long as the level is above the control point value, end I4a of the floating lever I4 is at the right of its norm position E-f-E, and the pressure in bellows 42 holds above the pressure in the bellows 45, in order to hold the nozzle and ilapper in their tangent relationship. The pressure in vbellows 42 being above that in bellows 45 causes the pressure in bellows 45 to continue to increase and, in effect, tends to increase the pressure in So, as the level lowers' toward the control point value, the measuring element IB moves the end I4a of the oating lever toward the neutral axis E-E with the result that, although the increasing pressure in the bellows 45 is tending to increase the pressure in the bellows 42, the movement of the measuring element IIJ is tending to decrease the pressure in the'bellows 42. But because the pressure in the bellows 45 will continue to change so long as the end I4a of the floating lever I4 is away from the neutral axis E-E, i. e., control point position, the instrument acts to prevent the level in the tank a from balancing out at any but the control point value.

Eventually when the control point value is reached under the condition of the assumed increased demand, the pressures in the two bellows 42 and 45 will be equal but will be above the previous value of 8 lbs. The pressure will be above the previous value of 8 lbs. by an amount required -to hold the valve g in whatever new position is 50 is adjustable tomatch the overall slowness of the process as described in the Mason application.

Returning now to the movement assembly, this fassembly is provided to facilitate (l) aligning the measuring element and the pen arm so that the pen arm points to the correct index on the chart of the value being measured by the measuring element I0; and (2) to facilitate setting the control point to the desired value.

Referring to Figures 1, 2, 3, ll, and 7, the movement assembly is supported on a base 52 secured to vthe instrument backing plate 53 (Figure 3). Secured to the base 52 by means of built-up posts 54 are inner and outer bearing supporting plates 55 and 55. These plates are provided with holes aligned on `the axis A-A, which holes serve as Vbearings for supporting the lever I'! and its asso secured the L-shaped pen arm support I8, for

supporting thepen arm I2. A shaft I'Ic passes through the section I'Ia, and supports a bearing sleeve I'id suitably xed to a hook-shaped section I'ie, and to the driving arm IIf of the lever I1. As shown in Figure 9, the lever I1 and the pen arm support effectively form a U-shaft. Pins 51 are provided on the U-shaft to enter the holes in the plates 55 and 56, which thereby support the Ushaft 1 The hook-shaped section lle has a friction drive surface I'Iig which by the spring action of section Ile presses against a shaft I'Ih, and normally holds the two sections llc and Ie against relative angular motion. The shaft I'lh is suitably rotatably mounted in the U-shaft, and is provided with a screw-driver slot. By rotating the shaft Ilh the angular relationship between the parts IIa and I'Ie may be adjusted.

This adjustment serves when necessary to brin the pen arm i2 into correct angular relationship with respect to the measuring element Ili. e.,it

serves to bring the pen and the measuring element into alignment at any convenient reference point, so that the pen always points to the correct positions on the chart for the different positions of the measuring element I0. The adjustment is made by applying to the measuring element Ill a known value of the variable which lthe measuring element I0 measures, and then rotating the shaft I'Ih until the pen arm I2 points tothe reference on the chart corresponding to the value applied to the measuring element I0.

Referring to Figure 2 (and to Figures 3, 4 and'7 for the details), the frame 2I supporting the bell crank 20 is pivotally mounted on the axis A--A between inner and outer supporting plates 58 and 59, suitably supported by the posts 54. The frame 2l is Vmade up of a U-shaped piece providing spaced inner and outer parallel arms 21a and 2 Ib, whose free ends are suitably spaced by a spacing column 2 Ic secured to the arms 2 Ia and 2 Ib. The frame 2l is pivotally supported from the plates 58 and 59 by pins 2Id (Figure 4), extending outwardly from the arms 2Ia and 2 Ib and entering suitable bearing holesin the plates 58 and 59, y

Returning to Figure 2, fixed to and extending forwardly from the frame 2| adjacent the pivoted end is an L-shaped arm. 2Ie which carries a.

control-point-setting indicating pointer 6I. v The forward end of the arm 2Ie turns downwardly and carries a pin which is journaled in a supporting plate 60 (Figure 3) supported by the part 54. The indicating pointer 6 I, secured to the arm 2 le is angularly adjustable with respect thereto by means of a conventional micrometer screw arrangement 62. The mechanism for angularly adjusting the frame 2I about the axis A-A to set the control point is described further on in the specification. The differential bell crank 20 supported b frame 2| is suitably secured to a shaft 20a, pivoted on suitable bearings in the frame arms 2Ia and 2lb. The driving arm 20h is connected to the driven arm IIa of the lever II by the link I9, and the-link I9 is of approximately the'same length as the distance that separates the axes A-A and B-B of the crank 2D and lever` II. The driven armY 20c of bell crank 20 is connected by link I3 to the end I4a of lever I4 as above described. The distance between the axis B'-B of the bell crank 20 and the point 0f connection 20d with the link I3 is the same as the distance that separates/the two axes A-A and B-B. Also whenthe controller is controlling the processat ana 1,520

"1l the control-point setting, the pointer connection 2Id is at the axis A-A.

Referring to Figures 2 and 3, the frame 2l is `adjusted about the axis A-A by a link 63 connected to an arcuate spring lever 64, pivotally supported at 65 on an extension of the supporting plate 58. The lever 64 is frictionally driven by its spring-pressed contact against a groove 66 in a control point setting shaft 61, journaled in inner and outer plates 58 and 60, and manually rotated by a control point setting knob 68. The

construction of the control point setting mechanism is described in more detail in the copending patent application` Serial No. 660,644, led April 9, 1946, now Patent No. 2,455,326.

When the condition being controlled is at the set point, asy determined by the position of the frame 2 I, the arm 20c of the bell crank'2il is parallel with the frame 2 i, and its connection point 20d with the link I3 is centered with respect to the axis A -A. Thus, the length of the link I3 --determines the` distance between `the center of motion A-A ofthe movementassembly and the neutral positionE-E of the vend Illa of the iioatingl lever I4.. As will be explained, provision is made to adjust the position of pin 22 with respect to the end I4a to align the operating parts. The control pointsetting mechanism functions as. follows: For agiven setting of the fra-me 2i there is a corresponding position of the measuring element, I6 that will position the differential lever 2U in its norm position with the point of connection 2Id aligned with the axis A-A. By rotating the control point setting knob 56, the frame 2| is vmoved about its pivot A-A, and its various positions require different corresponding positions of theV measuring element I in order to bring the differential crank 20 and the floating lever I4 into their norm position. Since the variousy positions that the measuring element assumes are determined by. the values of the condition being measured, the adjustment of the frame 2 l. about its axis A-A determines the set point at which the controller will maintain the process being controlled.

- The index pointer 2 le attached to the frame 2 I indica-tes the adjustment of the frame 2| with reference to the chart, and is so aligned with respect to the frame 2l that it points to the index on the kchart at which the controller will maintain the condition being controlled.

To align the indicating pointerei of the control point setting device accurately to indicate ,the .set point with, reference to the chart, the

control point setting Vknob 68 is turned to bring theA point of connection '20d in line with the axis lA A. The micrometer screw 62 carried by the L fshaped" extension 2id is then turned to bring the indicating arm 6l into alignment with the position of the pen arm I2. If desired during theV ladjustment of the micrometer screw 62, the arm Vnot change the relationship between the pen arm I2 and the indicating arm 6I.

The connections between the links and the bell cranks 'and the bearings supporting the'lever Il and crank '20 are made as irictionless as possible, and with a .minimum o'f lost motion, so that slightest movements of themeasuring 'element are accurately imparted to the oating lever I4. The construction of the movement assembly disclosed has several distinct advantages. One of them is that thealignment of theparts-is readily accomplished. Another is that only a single link I 3 is required between the movementv assembly and the control mechanism proper.v Another advantage is the concentric relationship between the pen, the index pointer and the connection point 2id of the differential crank 20, and the fra-me 2l, which provides that when thepenarm and indicating pointer El are aligned at one point on the chart scale, the alignment relationship holds inherently over the full scale. Further, with this construction the position of the` connecting link I3 is a measurepof the deviationbetween the pen arm and the indicating pointer 6I, which measure holds reasonably accurately throughout the working range ofthe instrument.

The nozzle-dapper desem-bl Thefdetails of the, nozzle-dapper assembly are best seen in Figures 3, 4, 5, 6 and' and 17. Refel-ring to Figures 3, a, and 7, the shaft 24, supporting the flapper and the dapper-operating lever 23, is freely pivoted between inner and outer supporting plates 73 and 1I, respectively, spaced apart by two spacing 4posts '12. The inner plate iii is secured to the posts by peening over the ends of the posts extending through the plate. The outer plate Ii and the posts 'l2 are secured r to the outer edge of a gear wheel 'I3 by screws passing through the gear wheel and threading into the posts. One of the screws 532Y is provided with a long head, which limits the extent of rotation of the gear wheel, as will be described. The plates if: and l! are provided with holes which freely receive the reduced ends of the shaft 24.

The dapper-operating lever 23 is secured to a sleeve 23a fixed to the shaft 24. A hair spring as shown in Figures 3 and 6, is xed at its inner end to the shaft 24, and at its other end to the post 'i2 adjacent the spring. The apper 26 comprises a thin phosphorous bronze at strip bent around the shaft 24 and soldered to it. In addition (Figure 6) the flapper is provided with a portion 26a bent back on itself and Ythreaded to receive a micrometer screw 26h by which the angular relationship between the iiapper 26 and the happier-operating lever 23 may be adjusted. lJhe flapper assembly is constructed and assembled to provide a substantially frictionless bearing support for the shaft 24.

IThe nozzle 2 is threaded into a hollow stud if., having a hex-shaped head 'I5 and mounted on the gear wheel i3. The stud 'ipasses through the gear wheel 13 into a passage 'el (Figure 1'7) in a frame casting i6, which forms a support for the control assembly and which provides various passages for air as will be described. The stud thus serves as the shaft for the wheel i3, and the passage Il the bearing for the shaft.

Between the gear wheel 'i3 and the frame i6 is placed a suitable gasket T8, which while permitting rotation of the gear wheel with respect to the frame i6, provides a seal which prevents air from escaping between the gear wheel and the fram-e T6. Referring to Figures 4 and 5, the gear wheel is held in place against the gasket 'I8 by means of an angle bracket 7S which presses against the end or" the hex head 15. The angle bracket 'IS is secured to the frame casting I6 by two screws Sathere being suincient spring in the l13 angle bracket 19 to hold the gear wheel 13 and the gasket 18 tightly against one another and against the casting 16.

Referring to Figures and 6, the gear wheel 13 is rotated by a pinion gear 88 which meshes with gear Wheel 13. The pinion gear 88 and wheel 13 have a 2:1 reduction and are mounted on a shaft 89 supported in the `frame casting 16. To the shaft 89 is secured a dial 90, Figures 1 and 3, and provided with indices which show the position of adjustment of the dapper-nozzle by reference to an index pointer 9i Turning dial 90 through 360 turns the gear wheel through 180.

The dial 90 is shaded as shown to indicate to the operator whether the instrument is adjusted for direct or reverse action. f

To prevent the gear wheel 13 from being turned beyond its extreme positions which are approximately 180 apart, one of the screws 92 Vsecuring the dapper-supporting frame 1I to the gear wheel Y 13 is extended as shown in Figure 3. Adjustable .screws 93 are provided to adjust the extreme positions of the gear wheel 13.

By mounting the nozzle and the flapper and flapper-operating lever on the gear wheel 13,

'the gear wheel 13 may be rotated to change the operative relationship between the operating pin 22 of the floating lever I4 and the flapper-operating lever to change the width of the proportioning'band of thecontroller, and to reverse the action of the controller as will be described. Also by mounting these parts on the gear wheel 13, the above-mentioned operative relationship may be changed without affecting the alignment of the nozzle and ilapper and their associated parts.

By utilizing the iioating lever construction and the free operating connection between the oating lever and the apper operating arm, the desired proportionality between the motion of the measuring element and the follow-up motor may be Vobtained by suitably shaping the cam surface of the ilapper operating arm. Also because the construction permits the free connection between the floating lever and the ilapper operating arm, the possibility of an inadvertent straining of the parts by the follow-up motor means or by the measuring element is eliminated.

l'Using the construction ofthe floating lever ,'Awith its ends operated generally at 90 directions by the measuring element and the follow-up motor, makes it possible to obtain the desired Ycorrespondence between the measuring element motion and the follow-up motor motionby the proper shaping of the cam surface of the iiapper operating arm, regardless ofi-whether the follow- .up motion imparted to the floating lever produces the Watts straight-line motion or whether it produces sorne motion appreciably departing from the straight-line characteristic.

However, with the construction disclosed which utilizes the Watts straight-line motion on the follow-up mechanism, certain advantages are obtained; Thus with the construction as disclosed, increasing pressure in bellows 42 always moves pin22 upwardly and so always tends to lift the ilapper from the nozzle, regardless vof whether the gearfwheel V'I3 is in its "reverse or direct acting position. Changing the gear wheel and yits associated partsvfrom reverse to direct ,acting position changes the direction of. the action of the measuring element on the operating lever 23 but does not change the direction of the A action of the bellows 42 on the operating lever.

Referring to Figure 6B, the three extreme posi- .tions` of Vthe lnozzle-dappermechanism aref' shown. In the extreme position entitled direct open and shut, the axis C-C of the nozzleflapper has been rotated to its lowermost position, in which position the dapper-operating lever 23 issubstantially Vertical. With this adjustment, as the measuring element I0 moves the end I4a of the floating lever I4 to the right of the neutral position E-E, the flapper 26 covers the nozzle 21, but the resulting increasing pressure in the proportioning bellows 42 in moving the floating lever I4 upwardly produces substantially no eiect on the apper-operating lever 23, because the contacting surface of the operating lever 23 is substantially` parallel to the line of motion of the operating pin 22. As the gear 13 is rotated clockwise to move the axis C--C of the flapper upwardly, a given movement by the end I4a of the floating lever I4 causes less movement of the operating lever 23, and a given movement of the lever I d by the proportioning bellows 42 causes more movement of the operating lever 23. Result-for a given motion of the measuring element I 0 rless change of pressure is required in the proportioning bellows 42 to maintain the nozzle and apper in their tangent relationship. Thus, movement of the gear wheel 13 in a clockwise direction effectively widens the proportioning band of the controller as defined in the above-mentioned Philbrick patent.

But rotation of the gear wheel 13 to the point where the flapper operating lever 23 is disposed in substantially the same horizontal plane as that of the operating lever pin 22 of the floating lever I4, as shown in the mid position view of Figure 6B, so arranges the parts that substantially no motion is imparted to the pin 22 by the measuring element. This position might be characterized as an innite proportioning band adjustment in which movement of the measuring element produces substantially no change of the output pressure of the controller.

When the gear wheel 13 is rotated to the ex'- treme position marked reverse onen and shut (Figure 6B) the axis C-C of the dapper is in its uppermost position and movement of the end lila of the noating lever I 4 to the right causes the dapper 26 to uncover the nozzle thereby causing the pressure in the bellows 42 to lower. But because the apper-operating lever 23 is substantially vertical in this position, movement of the oating lever I4 by the proportioning bellows 42 produces no effect and the instrument in this position of adjustment operates substantially as an open and shut controller. With this adjustment, the same movement of the element which produced an increase of outputpressure in the direct open and shut position now produces a decrease in pressure. As the gear wheel 13'is rotated counter-clockwise from its extreme position of reverse open and shut position. the proportioning band width of the controller is increased as previously described.

The desirability of adjusting the width of the proportioning band to match the control instrument to the process being controlled is fully described in the Philbrick patent and the Mason patent. The present construction .provides a simple and positive mechanism for accomplishing this adjustment.

The overall mechanism for adjusting the prof portioning band width may be described as follows: .The adjustment serves to vary the amount of pen travel required to change the output pressure of the 'controller mechanism between its maximum and minimum values. Because the 'movement'of the .dapper-with respect to the nozzle is only a fraction of a thousandth of an inch, the controller mechanism may be described as acting to move the operating pin-22 along a path just touching the flapper operating lever 23. Thus the path of movement of the pin 22. is determined by the slope of the operating (cam) surface of the rlapper operating lever 23.

Two components of motion move the pin 22. One is the motion of the measuring element that provides aV horizontal component of motion. rhe other is the motion of bellows 42 that provides a vertical component of motion. The ratio of these two components of motion is determined by the angle that the dapper operating lever 23 makes with the floating lever i4. When the angle is small the4 component of motion of the opera-tingA pin 22 due to motion ofthe behows 152 is small, and the component of motion due to movement of the measuring element is large, so that only a smally motion of theV measuring elelment is required to cause the output pressure of the controller to change between its maximum and minimum values'- But asf the angle approaches 90 the component'of motion produced 'by the measuring element is relatively small and -the component of motion produced by the bellows 42' is relatively large, and a relatively large motion of the measuring element is required tocause the output pressure of the controller to change between its maximum and minimum values.

It is thus apparent that rotation or" gear wheel 'I3 adjusts the angle that dapper-operating lever 23 makes with respect to floating lever I 4 and 4that this adjustment determines the amount of movement of the end Illa (by the measuring element) required to cause the output pressure of the controller mechanism to change between its minimum and maximum values.

The change from so-called direct action to reverse action is useful in instances where it is desired to have failure of air pressure either close a valve or completely open a valve. With the instrument capable of being operated either as a direct acting instrument or a reverse acting instrument, it may be applied to a type of valve motor which either opens or closes the valve with failure of air supply whichever action is desired.

The mechanical connection between theV meas-y uring element follow-up motor 42 and the flapper is constructed as a .Watts straight-line mecha-m ism in which movement of the floating lever Ill by bellows d2 imparts a straight-line motion to the operating pin 22. of the pin 22 bythe bellows 42 makesit possible to use a straight-line surface onA the operating face of the lever 23 while retaining the desired proportional motion between movement of. the measuring element and the movement of the bellows 22. By making the length of the lever E4 suiciently long so that the distance of the pin 22v to the axis D-D may be made relatively large, motion of lever I by the measuring element introduces no appreciable vertical componen-t of motionwto the pin 2.2 thereby aiding in retaining the. above mentioned proportional relationship.

Floating Zever Referring to Figures 2 and'3, to adjust the proportioning band width, the axis C-C of the napper and dapper-operating lever 23de adjustable around axis F--F (Figure 3)'. The axis of round operating pin,V 22 must coincide with. the .axis

This straight-line motion;

'F--F when theoperating pin'22 isfin a neutral position determinedby the neutral vertical and horizontal positions of the floating lever I4. These latter positions are determined by the neutral horizontal'position of end Ida, and the neutral vertical positionof end Mb. Since neither the neutral position of the end Ma nor of the end I4b is adjustable, provision is made for adjusting the operating pin-22 vertically and'hori- Vzontally with respect to the floating lever I4,

tobring the pin 22 into its neutral position concentric with the axis F-F.

To this end, referring to Figure '7, the lever I4 is made up in three sections. An upper section Illc is pivotally connected at Id to a lower section Me. Ihe angular relationship between the upper and lower sections I4c and Meis adjusted by a conventional micrometer screw arrangelment I4f, which connects a depending linger of section I4c with Ille.

A third L-shaped section Iig is pivoted at |471, on an.A extension of the lower section Ide', and carries the operating pin 22. The angular adjustment between the part I4g and the lower part Alignment of operating pin 22 and #appar-operating Zever 23 In order to adjust the operating pin 22 and the dapper-operating lever 23 so that they are properly centered, one with respect to the other, and properly aligned with respect to the flapper and nozzle, the control poin-t setting knob 68 (Figures 2 and 3) is rotated to move the frame 2| to bring the connection point 22d in line with the center of rotation A-A of the movement assembly, and an aligning pin is dropped through the holes S9 in the frame 2I, and driven arm 2Go of the bell crank 2Q. The control point index 6I is aligned with the pen arm I2 by moving the micrometer screw 62 on the con-trol point index.

Next, the proportioning band adjusting dial BIJ is rotated to place the gear wheel 'I3 in either of its open and shut positions so that the flapperoperating lever 23 is positioned vertically. Now (assuming a supply pressure of 1'7 lbs./ sq. in.) the micrometer screw M is adjusted toV move the operating pin 22 horizontally until the operating pin so positions the lever 23 as to produce an output pressure of from 3 to l5 lbs. per sq. in. as indicated by a pressure gauge, 93 (Figure 2), connected to the output of the relay valve by a pipe 94. During this operation, the restrictionadjusting arm 50d is moved to provide the least resistance possible between the bellows 42 and 45, so that any pressure diference between them is quickly dissipated.

The proportioning dial 99 (Figure 2) is now reversedvto move the gear wheel 'I3 to its other extreme open and shu-t position. If this reversal produces a change in the output pressure (taking it outside the 3 to l5 lbs. range) then by using equally.v the 'micrometer screw M and the micrometer screw 2Gb, and `by `going back and forth 'from the two extremeropen an-d shut adjustments of the .gear wheel 13, it is possible to 17; obtain an adjustment which keeps the pressure within the 3 to 15 lbs. range when the gear wheel 'I3 is in either of its open and shut positions.

To adjust the vertical position of the operating pin 22, the proportioning dial 90 is moved to place the gear wheel I3 in its mid-position between its two open and closed positions, in which position the operating-lever 23 is horizontally disposed. Now, the micrometer screw |4lc (Figure 2) is adjusted to bring the output pressure from the relay valve 3| to within the 3 to 15 lbs. range. The gear wheel 'I3 is now moved to first one of its open and shut positions and then its other open and shut position for the nal adjustments of the three micrometer screws 25h, Mk and |4f to keep the output pressure in the 3 to 15 lbs. range as the gear wheel 13 is shifted to its diierent positions.

As shown in Figures S, 4 and 5, the floating lever is suitably braced, and the shaft 4'! supporting the floating lever from the flexure spring 46 is mounted freely in suitable bearings. An adjustable stop lla is provided to prevent axial play of the shaft 4l.

Bellows assembly The exure spring 46 (Fig. 7) is clamped to a support formed in the frame casting l5. Secured to both sides of the flexure spring 45 are plates 95, provided with recesses 9@ to receive aligning studs 9! projecting from plates closing the free ends of the bellows 42 and 45. To the plates 95 also is suitably secured the frame or yoke 45h which supports the shaft 4'! of the floating lever I4.

Referring to Figure '7, each of the bellows 2 and 45 is made up of metallic bellows, the free ends of which are closed by plates |42 carrying the studs 96.

Referring to bellows 42, its fixed end is closed by a plate |44. Secured to and passing through the plate |44 is a rod |45, having a shoulder |45 to which the plate |44 is soldered. A larger hexshaped shoulder |47 extends from the rod, and the plate |44 is also secured to one side of this shoulder. The other side is clamped against the casting 16. The rod |45 extends into the bellows 42 and provides'a stop limiting the amount that the bellows can be compressed. The rod |45 extends out through the bellows and is threaded at The threads |45 thread into a hole |5] in |49. the casing which serves to tighten the shoulder against a gasket to provide an airtight mounting on the casting '56. A cover i5! closes the lower end of the hole |50. A passage |52 is provided through the shoulder portions of the rod |45, and connects the interior of the proportioning bellows with the hole |55 in the casting.' A passageway 4| in the casting l5 Aserves to connect the pipe 40 coming from the transfer switch with the hole |56, and so with the interior of the bellows 42.

Referring to Figures l, 3, and '7, Ahole |52 connecting with the interior Vof the'bellows is connected by a passage |53 in casting l with the pipe 49 going to the reset restriction 5G.

Reset bellows 45 (referring to Figure 7), is closed at its fixed end by a plate |54 to which is secured a rod |55, which performs several functions. It extends into the bellows, and provides a limit stop. It is bored at 55 to provide a passage into the bellows. It is threaded at l5? to receive a nut |59, which clamps the bellows to the casting l5. IThe casting is slotted at |53 (Figure 4) to receive the extension of the rod |55. To assemble the reset bellows in position, itis 18 necessary only to slide the rod extension |55 through the slot |58, locate the aligning stud 9'! in position, and tighten the nut |59.

Extending from the passage |55 is a flexible metal tubing 5|, which carries a conventional fluid-tight connection |62 (Figure 1) which is detachably secured to the end of the resistance 5i! opposite that to which the tubing i5 is secured.

Relay valve Referring to Figures 3 and 16, the relay valve is a complete unit removable from the casting 16 by taking out screws |55. The relay valve body is made up of an outer cover plate l, a body Illi, and an inner cover plate |02. A gasket |03 is provided between the cover plate and the body IUI, and a gasket |64 is provided between the body |0| and the inner cover plate |52. The three screws ||l5 pass through the relay valve and thread intothe frame casting 15, and hold the relay valve tight against the frame casting. A gasket |66 is provided between the inner cover plate |82 and the frame casting l5, and serves as a seal to prevent escape of air from the air passages that will be described going from the frame casting to the relay valve. The outer cover plate |50 is secured to the body |il| by three screws Referring to Figure 16, three screws ID3 hold the inner cover plate |52 to the body I0 E.

The restricted flow of air to the nozzle 2'! (Fig. 2) is supplied by the restrictor 29 mounted in the relay valve 3|. To this end, referring to Figures 2, 3, and 16, the pipe 32 supplying air to the relay valve is connected by conventional means to a port and passage |59 in the frame casting l5. The port and passage |55 enters the frame casting parallel to the front of the instru,- ment and runs into a passage l0, extending forwardly from the passage |05. As shown in Figures 14 and 15, the inner cover plate |92, the body Il, and the gaskets are provided with aligning passages Ia which align with the passage l0, which passage carries the air supply to a supply chamber formed by a cutout portion in the body |0| and by the gasket and outer cover plate |03 and IDU.

Referring to Figures 2 and 15, the restriction 25 which provides a restricted flow of air to the nozzle is embodied in the frame work of the relay valve 3|. The air is supplied to the restriction directly from the supply chamber Referring to Figure 15, threaded into a passage ||2 in the body IDI is a bushing |53 which carries a glass bead H4, provided with a small passage H5, which passage l5 forms the restriction that permits a restricted flow of air to flow to the nozzle. The passage I5 communicates with the passage l2 and with a passage 28h provided in the body lill, the gasket |54, the inner cover plate |027, gasket |05 and enters a nozzle Icapacity chamber 28a formed by a depression in the frame casting 16, and by the gasket |86 and the inner cover plate |02.

As shown in Figures 16 and 4, a passage 28 extends upwardly from the nozzle capacity through the frame casting 1S, then forwardly and then to the left through the casting 16 to the opening 11. The hollow stud 'I4 (Figure 1'!) conducts the air flow to the nozzle 21. I

Returning to Figure 15, to clear the restriction ||5 in the glass bead H4 from dirt or other foreign matter in the event that such becomes lodged in the restriction, a fine wire H5 is mounted on a plunger carried in a threaded sleeve H8, threaded into the body IBI as shown. A head H9 is provided on the plunger l1 for change of the output p-ressure in the chamber V|21 and in the proportioning bellows 4Z.

Referring to Figures 14 and 19, a preferred construction of the diaphragm 31 is shown. The diaphragm which is made of a suitable material such as .001i beryllium copper is cupped and is provided with radially extending depressions. Using this type of diaphragm, as the pressureY on the diaphragm increases, the amount of diaphragm movement or travel decreases for a given pressure change on the diaphragm. Also with the construction disclosed, the diaphragm has a relatively large motion for a relatively small pressure change back of the nozzle.

The nozzle capacity 28ctpreviously described, together with the restriction provided by the small hole |32, serves to damp out pneumatic oscillations which might otherwise occur under some circumstances due to the interactions of the nozale-flapper, relay valve, and proportioning bellows.

Transfer switch Returning now to Figure 2, the air piping system is shown with couplings |53 in the lines 32, 33 and 4|), which couplings may be broken so that (as shown in Figure l) the backing plate and control mechanism mounted on it may be removed from the easing.

As shown in Figures 2 and 18, the transfer switch 33 has four positions. The automatic p0- sition is shown in Figure 2, in which the `controller is connected to operate as has been described. To this end, a switch valve such as shown and described in the Mason Patent No. 2,476,104. is utilized. Such a switch valve. contains a base portion |64 which has six ports arranged as shown and connected with the piping as shown. Over the ports is a cover |5'provided with three internal grooves facing the base |64. These grooves are numbered respectively |53, |51, and |68.

In the automatic position groove |61 connects the ports connecting pipes 32 and 3ft, so that the air supply is delivered to the relay valve. Groove |55- connects the pipe 39 with the pipe il!) going to the proportioning bellows. It also connects a pipe dii with the pipe 39 coming from the relay valve, which pipe 8 goes to a diaphragm motor or other device.

When the cover |55 is turned to the manual position, as shown in Figure i8, the output pressure from the relay valve instead of being connected to the valve motor and to the proportioning bellows is dead ended. So although groove |61 still connects the supply p-ipe 34 to the supply pipe 32 going to the relay valve, the output pressure of the relay valve performs no control function. 1n this position, however, the groove |56 now connects the proportioning bellows 42 and the diaphragm motor with the pipe |19 connected. with the outp-ut side of -a conventional pressure regulator lll. The pressure regulator |1| is supplied with the regular air supply of 17 lbs/sd. in. through the pipe 35a, and is manually operated. by means of knob |12 to supply to the pipe I1!! any pressure desired below the supply pressure. A gauge |13 is connected to the line |11? to indicate the pressure from the line.

Thus, by turning the knob |12, any desired pressure may be supplied to the diaphragm motor. In practice, in starting up a process and getting it ready for automatic control, the transv fer switch 33 would be thrown to its manual position, and the pressure on the diaphragm valve vwould. be manually controlled through the regulator |1|V until Ythe process had been brought to a condition suitable to turn it over to automatic control. But because in the manual control position the transfer switch also supplies the air pressure to the proportioning bellows, the proportioning and reset bellows are exposed to the same pressure lbeing supplied to the diaphragm motor, just as when on automatic control.

When it is desired to throw the switch from manual control to automatic control after the process has manually been brought close to the set point, the control point setting mechanism is moved until the output of the relay valve 3|, as indicated by the gauge 93, is brought within the range of, for example, 5 to 10 lbs.

Because in this setting of the transfer switch, the control mechanism operates essentially as an on-oif controller, an output pressure between 5 and 10 lbs. indicates an almost exact alignment of the control point setting mechanism with the measuring element; i. e., the lever It as held by bellows 42 is moved by link I3 to bring the nozzle and flapper into tangency. Then when the transfer switch is later thrown to automatic position, the transfer is conveniently made without producing any material upset or change of pressure in the instrument, or on 'the diaphragm motor because ther nozzle and flapper are properly aligned in their operating position as they would have been held by the proportioning bellows 42 had the instrument been on automatic control. After the instrument is turned on to automatic control, the final adjustment of the control point setting is made to bring the control point to the exact value desired.

When the transfer switch is moved to test position as shown in Figure 18, the diaphragm motor is connected by the groove |66 with the output of the manual regulator so that the process being controlled is actually under manual control. The groove |61 still connects the supply pipe 3d with the supply pipe 32 going to the relay valve. The Ioutput of the relay valve is now fed back by the connection. of groove |36 to the proportioning bellows, but is not connected to the diaphragm motor pipe 48. This condition is useful when it is desired to test the instrument for various purposes while its measuring 4element is responsive to the process, but while its output pressure is not controlling the process.

When the transfer switch is moved to service position as shown in Figure 18, the supply pipe 32 'going to the relay valve is shut oir so that no pressure at all is delivered to the control instrument. The groove |14 connects the output of the manual regulator to the diaphragm motor so that the process may be manually controlled. But because no air is supplied to the control instrument, the entire control mechanism may be removed for repair or exchange leaving the process on manual control with the gauge |13 indicating the pressure being supplied to the diaphragm mot-or.

As many embodiments may be mad-e in the above invention and as many changes may be made in the embodiment above described, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative only and not in a limiting sense.

I claim:

1. In control apparatus including movable con dition-responsive means, control means having a member having a neutral position and operated by said condition-responsive means, in combination, a crank pivoteclV about a `iixed axis and 

